Environmental impact assessment (EIA) came into being in Nigeria with promulgation of the Act establishing three independent EIA systems—the EIA Decree 86 (1992), the Town and Country Planning Decree 88 (1992) and the Petroleum Act (1969). Despite a sound legal basis and comprehensive guidelines, evidence suggests that EIA has not yet evolved satisfactorily in Nigeria, as the current system amounts to duplication of efforts and cost. An evaluation of the EIA system against systematic evaluation criteria, based on interviews with EIA approval authorities, consulting firms and experts, reveals various shortcomings of the EIA system. These mainly include inadequate capacity of EIA approval authorities, deficiencies in screening and scoping, poor EIA quality, inadequate public participation and weak monitoring. Overall, most EIA study rarely meets the objective of being a project planning tool to contribute to achieving sustainable development and mitigate impact from development project. The work concludes on the suggestions to involve in EIA process relevant authorities and to increase the competence of EIA consultants.